Applying to MORE elite schools does not increase your chances of admission.
You have some sure things on your application list. Even so…I think you should read the thread I’m about to link. This VERY high achieving student was not accepted to any of the colleges to which he applied on his first round. He was a NMF, tops in his class, excellent ECs, etc. Even though he didn’t have a true sure thing for admission on his list, no one expected he would be shut out of admissions entirely but that’s what happened. And this was in 2005 when admissions were far less competitive than they are now.
Having a long list of elite schools doesn’t guarantee admission to elite schools.
Here is the thread, and I would suggest you read the whole thing.